1. Field of the Invention
This invention pertains to the technology of storage of liquids, including toxic liquids. More particularly, it pertains to a shut-off valve for use in pumping liquid into a storage vessel that shuts off the delivery pump when the tank becomes full.
2. Description of the Prior Art
Proper storage and handling of waste liquids, especially toxic liquids, has become very important because of the discovery that so many of them have been found to cause cancer and other serious diseases. Liquids that previously were treated as mere waste are now known to be highly dangerous to humans, as well as to the environment, and require careful and safe storage until they can be rendered harmless by further processing or become benign by passage of time.
The need to store these materials in leak-proof containers is now required by such government agencies as OSHA (Occupational Health and Safety Agency), the National Health Institute and others. A wide array of storage containers may be used, from small 1 and 2-gallon cans to large tanks, both underground and transportable. A container widely used in this situation is the standard 55-gallon drum; it is quite plentiful and its thick metal walls will safely store most materials.
These 55-gallon drums, along with other such containers, contain a standard, 2-inch diameter threaded aperture in the lid known as a "bung hole" that can be used for pouring or pumping liquid into the drum as well as to have test probes inserted thereinto for the purpose of determining various attributes of the stored liquid. Other openings are also formed in the top or lid of the drum. This same bung-hole type opening is also found in virtually all storage tanks from the very small to the extremely large. The rim of the bung hole usually contains a series of threads to accept a threaded plug known as a "bung".
One disadvantage in the use of storage tanks and drums, including the 55-gallon drum, is that they are so well sealed no light can penetrate the interior. In many cases no incandescent lamp can be safely used to aid one looking inside because the stored contents are either poisonous or highly combustible. Often the drum is pumped completely full of liquid and the pump is not shut down soon enough with the result that liquid spills out of the lid openings over the sides and onto the ground or other supporting surface to cause the toxic condition to become a problem all over again. Positioning a person to continually observe the level of fullness in the tanks raises labor costs and places him or her in a dangerous position near the toxic material.
A recent proposed change to the Uniform Fire Code states as follows:
"2-4.5 Piping and Ancillary Equipment 2-4.5.1 Means shall be provided for determining the liquid level in each tank and this means shall be accessible to the delivery operator. Provisions shall be made either to automatically stop the delivery of fuel to the tank when the liquid level in the tank reaches 95% of capacity or to sound an audible alarm when the liquid level in the tank reaches 90% of capacity."
The prior art has tried to deal with the problem of shutting off the flow of liquid into a tank, when the level reaches the uppermost safe point, but such attempts have not met with unbridled success. For instance, U.S. Pat. Nos. 559,555; 609,544; 968,362; 1,150,342; 1,427,793; 1,629,545; 1,188,535; 2,847,025; 4,493,337; and German Patent 2,148,868, as well as British Patents 20,399 and 828,125 all show float-operated shut-off valves that are mountable on a tank or boiler. However, in none of these devices may they be fully insertable through one opening, i.e., the floats are so large that they must be put inside the tank or boiler through a separate opening from that through which any other portion of the shut-off valve is inserted. In other of these devices, the liquid actually passes through the valve thereby requiring the valve to be removed, disassembled and cleaned before it can be used with other liquids.
Without portability, the devices become too costly to use. Bathing them in liquid requires dismantling and cleaning before reuse -- another costly process. Further, most of these prior art devices are rigidly fixed or mounted either internal or partially internal to the tank. Such mounting eliminates them from use rapidly between drums and prevents them .+-.rom being used as portable or "add-on" units.